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SCIENCE 



[N. S. Vol. XXXIV. No. 872 



resulting, not from observations made with 

 regard to any particular theory, but from 

 the simple collection of facts and the ar- 

 rangement of them in all possible ways, the 

 very method which has been despised and 

 condemned. Let us contrast with this the 

 method hitherto adopted, which has been 

 to hunt for some particular possible cause 

 which will give the eleven-year period. 

 Thus Professor E. W. Brown suggested- 

 in 1900 that the eleven-year cycle was due 

 to the tidal action of Jupiter, altered pe- 

 riodically by two causes : 



Mag. of 

 Period Force 



By Jupiter's eoeentricity . 11.86 years 0.33 

 By the motion of Saturn . 9.93 years 0.11 



and he suggests his contention by an in- 

 genious and striking diagram, which seems 

 to explain not only the main cycle, but its 

 anomalies. (This paper is, in fact, the ex- 

 ception above referred to.) But if his con- 

 tention is correct the periodogram should 

 show bright lines at 11.86 and 9.93 years, 

 which it does not. This is worth noting, 

 since it is sometimes said that there is noth- 

 ing new in Professor Schuster's method, 

 which is true enough in one sense, since it 

 is simply the analysis of Fourier. The 

 novelty consists (1) in calling attention to 

 the necessity of applying the analysis in 

 all cases, a necessity which I venture to 

 think was overlooked in this instance by so 

 able a mathematician as Professor Brown ; 

 and (2) in the insistence on the examina- 

 tion of all periods, irrespective of any par- 

 ticular theory or preconception. And in 

 this second character the method seems to 

 me to cut at the root of the canons of pro- 

 cedure which have found favor hitherto. 



As a second instance I present with 

 much more diffidence a few results which 

 seem to emerge from a very laborious an- 

 alysis of the rainfall at three or four sta- 



"^ Monthly Notices E. A. S., LX., p. 600. 



tions, for which Professor Schuster and 

 myself are jointly responsible. There is 

 some evidence for a cycle of 600 days in 

 the Greenwich rainfall to which a further 

 cycle in the quarter period (150 days) 

 lends support. On analyzing the Padua 

 records it is found that these cycles do not 

 exist, but it seems quite possible that there 

 are cycles of rather shorter period, viz., 

 594 days and 148^ days: the relation of 

 four to one being maintained. The sepa- 

 rate links in this chain are none of them 

 very strong, but they seem to hang to- 

 gether, and there is certainly a case for 

 further investigation. But would this case 

 have been likely to present itself in any 

 other way than by the examination of the 

 whole periodogram ? I find it very difficult 

 to think, even now the periods are sug- 

 gested, of any theoretical cause: to let the 

 facts speak for themselves took much time 

 and labor, but I venture to think that we 

 might have waited far longer, and cud- 

 geled our brains much more, before we got 

 the clue by formulating hypotheses of 

 causation. 



A new method is not adopted widely all 

 at once. Professor Whittaker has, I am 

 glad to say, begun to apply the method to 

 variable star observations, and is already 

 hopeful of having obtained valuable in- 

 formation in the case of the star SS Gygni. 

 Possibly we may hear something from him 

 at this meeting. Meanwhile I take the op- 

 portunity to remark that the history of 

 variable star observation affords us many 

 lessons as to the desirability of simply ac- 

 cumulating observations and letting them 

 speak for themselves instead of being 

 guided by a theory on hypothesis. Let me 

 give an instance. One of the fathers of 

 variable star-observing, the late N. R. Pog- 

 son, made a series of excellent observations 

 of the star B Ursce Majoris in the years 

 1853 to 1860. He then seems to have 



